A radiator for a vehicle may include an inlet tank adapted to receive coolant from an engine; an outlet tank disposed apart from the inlet tank and adapted to discharge the coolant back to the engine; a heat-exchanging portion fluidly connecting the inlet tank and the outlet tank and provided with a plurality of tubes and radiation fins to cool the coolant flowing in the tubes by exchanging heat with air; and a bubble separating unit connected to the inlet tank and adapted to separate bubble contained in the coolant discharged from the engine and to continuously discharge the coolant from which the bubble is separated to a reserve tank to supply the coolant from which the bubble is separated to the heat-exchanging portion.